A Sri Lankan woman who converted from Buddhism to Islam has been arrested by the authorities on suspicion of anti-state activities.
The woman, who is resident in the Gulf state of Bahrain, had recently written two books about her conversion.
They were written in Sinhala, the language of Sri Lanka's ethnic majority, who are mostly Buddhists.
She was on holiday in Sri Lanka when she was detained and is now being held in a police station.
The national police spokesman told the BBC he believed there were allegations that she was involved in anti-government or anti-state activities.
He did not know the details but remarked that although her name was Sinhalese, she was acting and wearing clothes in the manner of a Muslim woman.
Unconfirmed reports say that family members have tried to send lawyers but they have not been able to take the case to court - and that she has been detained under emergency laws.
The police spokesman told the BBC's Sinhala service that he did not have enough details to comment on the allegations. The police at the local police station where she is held have refused to comment on the case.
A report in the Bahrain-based Gulf Daily News named her as Sarah Malanie Perera and said she had lived in the Gulf state since the mid-80s.
But it said she converted to Islam in 1999 and that her parents and sisters also made the conversion.
The newspaper quoted her sister, also a Bahrain resident, as saying she was apprehended while trying to send books out of Sri Lanka through freight. A member of staff was linked to a Buddhist nationalist party and reported the book to police.
A member of the Muslim community in Sri Lanka said that Ms Perera had no pre-existing connection with Sri Lankan Muslims and the local community had nothing to do with the book over whose contents she was arrested.
He said she had been under arrest since Monday and had not yet been produced in court.
The BBC's Charles Haviland in Colombo says that Buddhist nationalism is currently an influential force in Sri Lanka and the party in question is part of the government coalition.
Sri Lankan Muslims are regarded as the third ethnic group in Sri Lanka occupy a respected and prominent position in society. But accounts of conversions from Buddhism to Islam are rare.